The present invention relates generally to an internal combustion engine having a combustion heater for heating related elements to the internal combustion engine and, more particularly, to an internal combustion engine having a combustion heater in which the air for combustion is introduced into the combustion heater via an intake passage of the internal combustion engine.
In the internal combustion engine, an operability is deteriorated with an increased friction in a low-temperature state, and with this deterioration a fuel efficiency worsens as well as causing an increase in noises. Further, there arises a problem, wherein a related device operating in connection with the internal combustion engine such as, in a vehicle, for example, a car room heater with the cooling water of the internal combustion serving as a thermal source, is deteriorated in its function when the internal combustion engine is at the low temperature, i.e., when the temperature of the cooling water is low.
Accordingly, it is required that the internal combustion engine be provided with a heating device for increasing the temperature of the internal combustion engine itself or a temperature of the related element to the internal combustion engine itself when in a warm-up process after a start-up or when an exothermic quantity of the engine itself is small. This necessity is remarkable especially in a diesel engine with a small exothermic quantity and becomes more remarkable with a tendency of further gaining the fuel efficiency in recent years.
Such being the case, Japanese Patent Laid-Open Publication No. 62-75069 discloses a technology of enhancing a starting characteristic by speeding up the warm-up of the internal combustion engine. According to this technology, a rise in temperature of the internal combustion engine body is speeded up by speeding up a rise in temperature of the cooling water by providing a combustion heater for heating the cooling water. In this technology, the attention is paid to a temperature when starting the internal combustion engine. In addition to the starting time of the internal combustion engine, however, the temperature of the internal combustion engine becomes comparatively low also when the exothermic quantity of the internal combustion engine itself is small, e.g., when a quantity of fuel burned in the combustion chamber is small. In such a case also, it is advantageous to the internal combustion engine itself or the related element thereto to provide the combustion heater.
Incidentally, although the combustion of the combustion heater continues also during an operation of the internal combustion engine for a short while after the start-up thereof, at this time the combustion heater introduces the combustion air from the intake passage of the internal combustion engine.
On the other hand, in the internal combustion engine, compression leakage of the mixture is protected by a piston ring provided in a gap between the cylinder and the piston. However, since the mixture absorbed in the cylinder is compressed with high pressure, a small quantity of an unburned gas before combustion is blown in a crankcase from the gap between the cylinder and the piston. This is a so-called "blow-by gas". This blow-by gas includes oil in the crankcase. As is well known, a blow-by gas introducing passage for introducing a blow-by gas into the intake passage may be provided in the internal combustion engine, in order that the blow-by gas returns to the cylinder and the unburned gas is burned. However, depending on a position in which to introduce the blow-by gas into the intake passage, there exists such a possibility that the blow-by gas might be introduced together with the combustion air into the combustion heater, and inconveniences such as deteriorations of combustion and of ignition in the combustion heater might be caused due to contaminating components such as an oil contained in the blow-by gas.